1. Field of the Invention
This invention relates to apparatus for mobilizing of human limbs.
2. Description of the Prior Art
In recent years, there has been an increasing awarness of the advantages of mobilization of human joints as a part of the orthopedic care which follows an injury, an illness, or a surgical procedure. A joint can stiffen rapidly as a result of the immobilization, and in many cases extensive therapy is required in order to regain full use of the joint after it has stiffened. In the rehabilitation of human joints, therefore, it has been found useful to keep those joints mobilized by means of a device that continuously forces the limb to move, slowly and over a period of many hours.
Devices that perform this function have been developed and are commercially available. These devices, which are usually referred to as "continuous passive motion" (CPM) devices consist generally of a motorized frame or carriage in which the affected limb is held by gravity or by straps, and a control circuit that enables the clinician to start and stop the device, to adjust its speed, and to determine the extent of the motion by setting a maximal flexion and a maximal extension position.
Various forms of muscle stimulation have also been developed for therapeutic purposes in the treatment of limbs and joints. Both direct muscular stimulation and neuromuscular stimulation (NMS) have been used.
Direct muscular stimulation describes the action upon a living muscle or group of muscles by an extraneous agent for the purpose of causing said muscle or group of muscles to contract. This is particularly useful in those cases in which the muscle or group of muscles cannot fully or partially contract because of disease or trauma. The extraneous agent can be a chemical substance, a mechanical, thermal, or electrical impulse, or any other action that will interact directly with the contractible fibers and cause them to contract. In the context of the present application direct muscular stimulation is construed to mean electrical muscular stimulation because stimulation of muscle tissue is best and most controllably achieved by means of pulses of electric potential applied in the vicinity of the muscle or group of muscles one wishes to stimulate. In any embodiment of this invention in which direct muscular stimulation is called for, electrical muscle stimulation preferably will be employed.
Neuromuscular stimulation is the indirect stimulation of muscles or groups of muscles effected through the mediation of those nerve fibers that innervate them. Obviously, neuromuscular stimulation can only occur when the muscle or group of muscles one wishes to act upon is innervated, i.e. at least some of the nerve fibers that are normally connected to it are intact and the connection is viable. The advantage of neuromuscular stimulation over direct muscular stimulation is that nerve fibers have a lower stimulation threshold and thus neuromuscular stimulation can be effected with lower energies and more easily. Many chemical and physical actions can effect neuromuscular stimulation, but electrical neuromuscular stimulation is preferred because of the precision and ease with which an electric potential pulse can affect a nerve. In the context of this application, electrical neuromuscular stimulation preferably is meant whenever neuromuscular stimulation is referred to as part of an embodiment of this invention.
The concept has been introduced of coupling a neuromuscular stimulation (NMS) device to a CPM device, thus providing what has been called "continuous active motion" (CAM). The clinician thus has the option of either moving the limb passively with a motorized device, or making the limb move autonomously by causing the limb's muscles to contract, or to do both. In a copending patent application entitled "NMS Aided Continuous Passive Motion Apparatus" by T. C. Wright and S. H. Ober, Ser. No. 578,470, filed Feb. 9, 1984, which is assigned to the same assignee as the present application, a system is shown in which the CPM carriage is paused when maximal extension is reached. The NMS device is then turned on for several seconds and, after that, movement of the CPM carriage back toward maximal flexion resumes.
The technology of CPM and CAM, once accepted by the medical profession and implemented with convenient and economical apparatus, is not limited to the mobilization of diseased or traumatized joints. There is evidence reported in the literature that CPM improves the circulation of blood in the affected limb and prevents venous stasis and thrombosis. It can also be inferred that CPM and CAM may be beneficial in the as yet unexplored cure and prevention of several afflictions of bone, tendons, muscles and other structures of human limbs.